1. Field of the Invention
The present invention is directed generally to a composition and method for providing increased particle cohesiveness and durability and, more particularly, to a material conditioner and stabilizer and method thereof.
2. Description of the Background
In the United States alone, there are more than 1.5 million miles of unpaved roads and streets compared to just over 3.9 million miles of paved roadways. Unpaved mileage can include graded and drained roadways made of natural earth, gravel, stone, slag, shell or similar materials. These roadways are often aligned and graded to permit use by motor vehicles. In addition, there are thousands of miles of unpaved areas such as construction sites, parks, parking lots, racing tracks and mines.
Two of the most prevalent problems associated with unpaved roads are: (i) controlling traffic generated dust; and (ii) maintaining stability and strength of roads throughout the year.
Traffic generated dust from unpaved roads contributes significantly to airborne particles which degrade agricultural produce, cause respiratory problems, increase wear and tear on vehicles, and result in a higher rate of deterioration of the roadway. Reducing dust improves drivers' sight distance, reduces effects on adjacent roadside stream habitats, decreases the number of motor grater bladings needed to improve ride quality, and decrease the loss of surface aggregate.
The strength of unpaved roads undergoes significant fluctuations during the year due to the continuous variations in soil conditions. Stability and load-bearing capacity of unpaved roads depends mainly on shear strength of soil that, in turn, depends on the soil type. For example, under wet conditions, sand has an adequate cohesion due to the capillary stress, by which it has a sufficient load-bearing capacity. Under dry weather conditions, however, sand particles lose cohesion and separate, and the load-bearing capacity can be reduced to almost zero. Clay, on the other hand, develops considerable cohesion in dry conditions, and has a high load-bearing capacity, which however, rapidly decreases with increased moisture content. Adverse climate and loading conditions, such as freeze-thaw variations and alternating dry-out shrinkage and wetting/swelling, can result in the formation of waves, transverse corrugations, rutting, and shoving. These types of formations are often referred to as wash-boarding for their distinctive appearance.
The various native soils encountered in road building and other load bearing applications often lack the mechanical properties required for satisfactory results. Inadequate soil strength can also lead to defects in the road surface, such as rutting, corrugation, cracking and failure of pavement and gross shifts in the load surface. Poor water absorption properties of clay soils can lead to heaving, surface failure, seasonal shifts, extrusion of base material and other problems.
Soils too weak to bear the anticipated load can be stabilized by the addition of materials which impart mechanical strength, such as aggregate, and by the addition of chemical stabilizers, which decrease water absorption and increase the cohesion of the soil matrix by forming a cement-like compound to hold the matrix together. The appropriate type of stabilization and results to be expected depend upon the soil types encountered and methods of application of the stabilizer and construction of the road. A range of soil compositions can serve as good road base material, but high strength, resistance to shear and resistance to erosion or swelling by water are required. Most native soils require some extent of stabilization to achieve the goals and provide a proper material for road construction.
Several compounds have been used to stabilize soils, especially those intended to be a road surface, including calcium chloride and petroleum resins. Calcium chloride is a naturally occurring brine used for dust control and soil stabilization. The compound is hygroscopic, exhibiting a string moisture film, high surface tension, and low vapor pressure assisting in the binding of aggregate particles. A major limitation of this compound is its narrow application range. If the calcium chloride solution is applied at a less than specific dilution ratio, the effectiveness of the compound is diminished, while application at a higher than necessitated dilution ratio causes beading on the application surface and thus prevents treatment of the target soil.
Petroleum resins generally consist of a concentrated, non-volatile emulsion consisting of about 60% semi-liquid natural petroleum resins and 40% wetting solution. Although these products are effective dust retardants, overall soil stabilization is poor given the limited penetration of the resins into the soil profile. Petroleum resins may also be less environmentally friendly making their use prohibited in certain situations.
Therefore, the need exists for an environmentally friendly, water soluble chemical composition that can be used as a material conditioner and stabilizer.